The objective of this project is to examine the role of cyclic nucleotide phosphodiesterases (PDE) in the regulation of cyclic GMP metabolisma nd of salivary secretion in therat submandibular gland. The following physiological, biochemical and pharmacological studies will be performed: 1) PDE will be partially purified and characterized in terms of its subcellular distribution, substrate selectivity, kinetic properties (Km and Vmax), and ionic requirements. 2) The changes in activity and kinetic properties of PDE will be measured following stimulation with cholinergic agents. In addition, the level of cGMP, the activity of membrane-bound ATPases, and the extent of K efflux and uptake will be measured in resting and stimulated glands and the results correlated with the PDE measurements. 3) Similar measurements will be made on the glands of ganglioectomized and reserpine treated rats in order to further investigate the autonomic regulation of cyclic nucleotide metabolism and to evaluate models of altered nucleotide metabolism as a reason for abnormal secretory responses. These studies will be an extension of preliminary investigations suggesting that cGMP may be involved in activation of ion pumps and that PDE activity is altered after chemical sympathectomy with reserpine. We propose to test the hypothesis that the time course and magnitude of the cGMP response induced by cholinergic stimulation is modulated by a PDE sensitive to CA++ calmodulin. Further, that cGMP stimulates a protein kinase which regulates the activity of membrane bound ATPases, particularly (Na+ + K+) ATPase. Alteration in PDE activity by drug or disease lead to disturbances in the secretory response and in the characteristics of the secretory products. This will alter the physiological functions of saliva and its role in the maintenance of oral health. Our long term objective is to elucidate the coupling mechanisms underlying the secretation of water and electrolytes insalivary glands.